Ignition device.



L. H. GIBSON.

IGNITION DEVICE.

TloN FILED AP 24 Patented May 1, 1917.

l'Unrrnn eraf/ins PATENT onirica.,

LESTER H. GIBSON, 0F BROOHLINE, MASSACHUSETTS, ASSGNOR 'lO GIBSON-HOLLSTER MANUFALCTUBING COMPANY, F BOSTON, MASSACHUSETTS, A CORPORATION "7 MASSACHUSETTS;

. pplication tiled April 24 To all whom t may concern:

Be it known that I, Lnsfi'nr H. GnsoNya;

tion Devices; and l do hereby declare 'the following to be a full, clear, and exact description o' the invention, such as will enable others skilled in the art to which it appertains to make and use the sa me.

The present invention relates'to ignition devicesand more particularly to spark plugs employed for exploding a charge ot gas in the combustion chamber of an internal combustion motor.

In certain types of spark plugs the spark occurs at the opening of a chamber formed in the spark plug, igniting a small body of gas contained in the chamber, which in turn ignites the main body of gas in the combustion chamber, rlfhis type of plug is satisfactory in that the passage of gas past the sparking points tends to clean the points and prevent the accumulation of oil or carbon thereon. ln spark plugs of this type, however, it frequently happens that a body of inert or burnt gas collects in the inclosed chamber and prevents the formation of a body of combustible gas about the spark gap.

The object Lof the present invention is to l. provide certm'n improvements in a Spark plug of this type to permit the passage of combustible gas to the spark gap and insure that the main body of gas shall be exploded by the spark.

VVitlVthis object in view the features of the invention consist in certain novel teatures of construction, combinations and ar rangements of parts hereinafter described and claimed, the advantages of which will be obvious to those skilled in the art from the following description.

In the accompanying drawings illustrating the preferred form of the invention; Figure 1 represents a longitudinal section in elevation of a spark plug embodying the features of the invention; F ig. 9. is a bottom plan view ot theplug shown in Fig. l; Fig. 3 is a detail showing a section ot' the lower end of the plug and illustrating` the passage for the gas; Fig. 4 is a detail illustrating the method of forming the insulating shell of mica for the high tension electrede; Fig. 5 is a detail showing the method Specification of Letters Patent.

IGNITION DEVICE.

atented May i, l 917.

, 15H5. Serial No. 23,585.y

ot' inserting the mica shell in the porcelain bushing; Fig. Gis a detail illustrating a modified form of the plug; and Fig. 7 is a plan view of the plug shown in Fig.

The spark plug shown-in the illustrated 60 embodiment of the inventionJ consists oi' a metal shell l having a depending rnnular skirt 2 which is threadedly received in the cylinder of the internal combustion motor.`

The skirt or the plug forms a substantially inclosed chamber 3 having side walls which converge to a restricted orifice 5. A small body of combustible gas collects in the chamber 3 and is exploded by a spark in the orifice 5, this body of gas then rushing out through the orifice and explodingin turn the main body ot' gas in the combustion chainber. The usual high tension electrode (i is mounted in a porcelain bushing and connected at its upper end with a terminal `cap S.

rlhe insulator bushing is secured in the metal shell by a gland l() threadedly engaging with the metal shell l and yieldingly clamping the bushing in the shell through copper asbestos washers 12. high tension electrode G is provided with an insulating shell consisting of a sheet of mica 1l wound cylindrieally thereon. ln forming the mica shell, as shown clearly in Figs. #and 5 of the drawings the sheet of 85 mica is wound Closely upenn mandrel 13 having a longitudinal slot 15, and the mandrel and shell are then inserted within the porcelain bushing, the mandrel being then withdrawn to permit the insertion ot the 99 seal 16 of perhigh tension electrode (S. manently flexible cement surrounds the electrode and serves to `prevent the. passage of gas from the combustionchamber between the electrode and insulating members. rllhe lower end of the electrode extends into 'the orice 5 and the spark passes between the electrode and the annular rim of the skirt 2 ot' the metal shell.

it 'frequently` happens in.spark plugs of 100 this type that a body of inert gas collects in the chamber 3 and upon the ocrln'rence of' the spark the resulting explosion is not sutilcient to properly ignite the main body of gas in the combustion chamber owing to the Q05 the skirt 2 and intersecting Vthe spark gap to 110 The 8o permit the access of combustible gas to the spark gap. In the illustrated embodiment of the invention a slot or passage 1'? extends transversely across the lower face of the skirt and intersects the spa-rk gap, as shown clearly in Figs. l and 2. In the illustrated embodiment of the invention one of the sparking points is conveniently formed by a non-corroding ring 18 of nickel which is inserted in the lower face of the skirt and forms the rim of the orifice 5. The transverse slot or passage 17 extends across the face of the skirt and the ring 1S, and lthe ,spark passes between the electrode 6 and the face of the ring 18 across the passage.

In lthe modified constructi'n shown in Figs. 6 andi'7 the skirt Q, the electrode 6, and the slot 17 are formed in the usual manner and the opposed sparking points are conveniently formed by metal pins 20 secured` in the skirt 2 and disposed upon opposite sides of the electrode 6 to cause the spark to pass across the transverse slot 17.

lVhile it is preferred to employ the specific construction and arrangement of parts shown and described, it will be understood that this construction and arrangement is not essential except so far as specified in the tending through the bushing and having a sparking-point located in the orilice, 'the restricted orifice compelling the ignited gas in the chamber to pass and clean the sparking points7 and the lower :lace of the shell foi-nr ing a substantially flat annular surface around the orifice and being provided with a slot cut therein and intersecting the orifice near the sparking points to permit vl'ree access of combustible gas te the sparking points.

2. A spark plug comprising a metal shell having a depending annular skirt forming an inclosed chamber with a single restricted orifice at its bottom, the inner face of which forms one of the sparking points, an insulat ing bushing secured the shell. and an electrede extending through the bushing and having a sparking point located in the orifice, the passage of the ignited gas past the sparking points tending to clean them, and the lower face of the shell being provided with a slot cut therein and intersecting the oriiice near the sparking points to permit free access of combustible gas to the spa-rking points.

3. A spark plug comprising a metal shell having a depending annular' skirt. the bottom of which is thickened to forni an inclosed chamber `with a single restricted oriice at its bottom, the skirt forming a substantially flat annular bottom surface for the plug around the orice, an insulating bushing secured in the shell, an. electrode extending through the bushing and having a sparking point located in the orifice, and a noncorroding ring inserted around the mouth of the orifice and flush with the bottom surface of the ping to form the other sparking point, the inclosed chamber compelling'the ignited gas to pass and clean. the sparking points, and the lower face of the shell being proiided with a transverse slot eut therein and partially through the ring to intersect the -orii'ice near the sparking points and permit the free access of combustible gas to the sparking points.

LESTER H, GBSON. 

